Cyclic acetals of unsaturated aldehydes



Patented Aug. 28, 1945 oYoLIc ACETALS F UNSATURA'IED ALDEHYDES MurraySenkus, Terre Haute, Ind., assignor to Commercial SolventsCorporation,"1erre Haute, Ind., a corporation of Maryland 1 No Drawing.Application May 1'7, 1943, Serial No. 487,335

8 Claims. (Cl. 260-338) The present invention relates to new and usefulcyclic acetals of unsaturated aldehydes. More particularly, it isconcerned with cyclic acetals having the following general formula:

in which R may represent hydrogen, a-hydroxyakyl, or an alkyl group; Bmay be either alkyl, aryl, furyl, or hydrogen; R. represents hydrogen,aryl, or alkyl; and Rfimay be .eitheralkyl or aryl, the substituents Band R representingthe following combinations of groups respectively, andno others: hydrogen and aryl, alkyl and alkyl, aryl and alkyl, and aryland aryl.

Unsaturated -nitro-1,3-dioxanes included by the above formula are:5-nitro-5-methyl 2-(1- methylstyryl)-1,3-dioxane, 5-nitro-5-methyl 2-(l-phenylstyryl) -1,3-dioxane, 5-nitro-5-ethyl-2- (l-methyl-l-butenyl)-'1,3-dioxane, 5-nitro-5-hydroxymethyl-2- (1 -ethyll-pentenyl) -1,3-dioxane, 5-nitro-5-ethyl-2- l-ethyll-pentenyl) 1,3-dioxane,5-nitro-2-(l ethylstyryl)-1,3-dioxane, 5-nitro-5-hydroxymethyl-2-styryl-1,3-dioxane and the like.

Compounds of the above type are prepared by distilling a mixtureconsisting of a suitable polyhydroxy nitro compound and the desiredunsaturated aldehyde in the presence of a small amount of an acidcatalyst, such as concentrated hydrochloric acid, sulfuric acid, orbenzenesulfonic acid. Generally, it will be found desirable to carry outthe reaction in the presence of a liquid capable of removingthewater-produced during the condensation, as a constant boiling mixturewith said liquid. Benzene and toluene are typical examples of suchmaterials.

The compounds produced in this manner may be obtained in a relativelypure state by washing the crude reaction mixture with a suitablequantity of water. If necessary, a dilute solution of a weak alkalinematerial, such as sodium carbonate, may first be-employed to neutralizethe acid catalyst present, followed by washingwith water to remove anyadditional impurities. The liquid cyclic acetals produced in suchinstances are preferably dried over a solid dehydrating agent, such ascalcium chloride or anhydrous calcium sulfate, and then distilled.However, these compounds may also be dehydrated by distilling the samewith benzene or similar organic liquids. The compounds of the presentinvention, which are normally solids at room temperature, are

desired, with-a dilute solution of sodium bicarbonate, followed bytreatment with water. Upon cooling, the solid product thus obtainedmaybe separated from the reaction mixture by filtration, I

or any other satisfactory means, after which they may be convenientlypurified at temperatures slightly above their melting point by washing,if

further freed from impurities by recrystallization from a solvent, suchas methyl alcohol, ether, benzene, and the like. Colored impurities ineither the liquid or solid products may be effectively removed by meansof heating the same in the presenceof small quantities of finely-dividedcharcoal or other decolorizing substances.

The unsaturated cyclic nitro acetals of-my invention possess certaincharacteristics that serve to readily distinguish them from any-otherunsaturated cyclic nitro acetals as well as the unsaturated cyclicacetals prepared from unsaturated aldehydes, of the class employed inthe present invention, and unsubstituted glycols. One of the moststriking of such characteristic differences is the fact that underidentical conditions of catalytic liquid phase hydrogenation, thecompounds of the present invention yield unsaturated cyclic aminoacetals; whereas in the case of the unsaturated cyclic nitro acetals notincluded .within the scope of my invention, as well as with theunsaturated cyclic acetals prepared from unsaturated aldehydes andunsubstituted glycols, such compounds are completely saturated as theresult of such treatment.

Polyhydroxy nitro compounds which may be employed in the presentinvention may be any of such compounds which are capable of formingcyclic acetals under the described conditions, and

it is to be understood that the expression polyhydroxy nitro compoundsis to be interpreted as such. More specifically, these compounds may berepresented by the following general formula:

The aldehydes which may be utilized in the,

preparation of these cyclic acetals of the present invention may berepresented by the general formula:

RCH='CCHO i in which R. may represent an aryl or an alkyl hydes includedby such frmu1a.. are: a-BthyhB- methylacrolein,m-methyl-B-ethylacrolein, cinnamic aldehyde, a-methylcinnamic aldehyde,'a-ethylci-nnamic aldehyde, u-phenylcinnamic aldehyde and the like. Theexamples which follow are illustrative of the present invention.

Example I -nitro-5-ethyl 2 1 methyl 1 'butenyl) 1,3-dioxane was preparedby distillinga mixture consisting of 126 parts of a-me'thyl-p-ethylacroaethyl ,3- propylacrolein,

drogenation at a pressure of 1500 lbs. per square inch fora period ofthree hours at a temperature of between fill-70 C. Throughout thehydrogenation step, the mixture was constantly agi- I 'ftated. Afterabsorption of hydrogen had ceased, ..the reactionanixture was removedfrom the apparatus, the catalyst separated from the solution byfiltration and the methanol removed from the filtrate by fractionaldistillation. The 5-aminof5-ethyl-2--(l ethyl-l-pentenyl)-1,3-dioxaneobtained in this manner amounted to 80 parts and boiled at 105-108" C.(1 mm). The product was acolorless, odorless, mobile liquid, and wassolulein, 149 parts of 2-nitro-2-ethyl-1,3-propanedio1,

250 parts of benzene, and 0.5 part of concentrated sulfuric acid.Heating was continued until substantially all of the water producedduring the acetal formation was removed, together with the benzene, inthe form of a constant boiling mixture. The crude reaction mixture, thusobtained, was then distilled under reduced pressure, and the fractionboiling at 115C. (2 mm.) collected. This portion consisted ofsubstantially pure 5-nitro-5-ethyl-2-( l-methyl-l-butenyl) -1,'3-dioxane, a colorless liquid having a. specific gravity ((120 of 1.0852,and a refractive index m oflxi'llll. v

Analysis: Calculated for C11H19NO4: N, 6.11. Found: N, 6.39.

Example II A mixture consisting of 137 parts oftris(hydroxymethyDnitromethane, 132 parts of cinnamic aldehyde, 300parts of benzene and 1 part of concentrated hydrochloric acid was heatedgently until all of the benzene, together with the water produced by theformation 0f the acetal, had been completely distilled off. The reactionmixture, thusobtained, solidified, and the crude 5 nitro 5 hydroxymethyl-,2 styryl 1,3, dioxane, purified by recrystallization from benzene. Thepurified product/melted at 149.8 C., and was obtained in a conversion of45 per cent.

Analysis: Calculated for CiaH sNos: N, 5.26. Found: N. 5.10.

, ExampleIII One hundred and twenty-six grams of u-ethylc-propylacroleinand 149 grams of 2-nitro-2- ethyl-1,3-propanediol were reacted inaccordance with the procedures described in the above examples,resulting in the formation of 150 grams of 5 nitro 5 ethyl 2 (l methyl 1pen teny1)-1,3-dioxane, boiling .at l271-28 C. (1 mm). This product wasacolorless and odorless liquid soluble in ether, benzene, and methanol,

One hundred forty parts of 5-nitro-5-ethyl-2- (l-ethyl-l-pentenyl)-1,3-dioxane, 300 parts of methanol, and 5 partsof Raney nickel catalystwere placed in a suitable hydrogenation unit and sealed. This mixturewas then subjected to hyble in methanol, ether and benzene, butinsoluble in water. Analysis: Calculated for C13H25NO23 N, 5.17. Found:N, 6.22. The structure of the aminoacetal thus 'produced was determinedby dissolving 15 grams of the latter in 128 gramsof 8 per cent sulfuricacid and allowing the resulting solution to standovernight. Thistreatment caused the acetal to hydrolyze into the aminohydroxy compoundand an aldehyde. The latter rose to the top in the form of an oil andwas separated, dried over sodium sulfate and distilled. The aldehydeobtained in this manner boiled at 173 C. (5'50 mm), which is the boilingpoint of a-ethyl-,c-propylacrolein.

In a separate experiment, a mixture consisting of parts of2-(1-ethyl-1-pentenyl) 41,3- dioxane, 400 parts of methanol and 10 partsof Raney nickel catalyst was subjected to hydro genation underconditions identical with those utilized for the reduction of5-nitro-5-ethyl-2- (l-ethyl -l-pentenyl)-1,3-dioxane. On completion ofthe hydrogenation, the vz-(l-ethylpentyl) 1,3-dioxane, thus produced,was separated in the .usual manner from the catalyst and solvent.Determination of the extent of reduction was carried out as previouslydescribed. 'Thealdehyde isolated in this manner boiled at 163 C. (750mm), indicating the presence of substantially .pure 2 ethylhexaldehyde.This observation proved conclusively the complete reduction of theabove-mentioned unsaturated cyclic acetal.

Cyclic 'nitro :acetals of unsaturated aldehydes, prepared as outlinedabove, are either colorless liquids or white crystalline solids, and aresoluble in the common organic'solvents, such as methanol, acetone, andbenzene. They have been found to be useful as intermediates in the preparation of various surface active agents. Such compounds are similarlyuseful as reagents in the synthesis of numerous other valuable organiccompounds such as the corresponding unsaturated amino dioxanes which maybe prepared in accordance with the procedure described in my copendingapplication, U. S. Serial No. 487,336, filed May 17, 1943. Additionaluses for such products will readily occur to those skilled in the Myinvention now having been described, what I claim is:

1. Cyclic acetals having the following formula:

wherein R is a member of the group consisting of hydrogen, alkyl, andu-hydroxyalkyl; R is a member .of the groupconsisting of hydrogen,alkyl, aryl and furyl; R. isa member of the ,group hydrogen, aryl, andalkyl; and R is a member of the groupalkyl and aryl, the substituents Rand R representing the following combination of groups and no others:hydrogen and aryl, alkyl and aryl, alkyl and alkyl, and aryl and aryl.

2. 5 nitro 5 ethyl 2 (1 ethyl 1- pentenyl) -1,3-dioxane.

3. 5 nitro 5 ethyl 2 (1 methyl 1- butenyl) -1,3-dioxane.

4. 5 nitro 5 hydroxymethyl 2- styryl- 1,3-dioxane.

5. In a process for the production of cyclic acetals of unsaturatedaldehydes, the step which comprises reacting an unsaturated aldehydewith a polyhydroxy nitro compound in the presence of an acid catalyst,said polyhydroxy nitrocompound having the formula:

in which R is a member of the group consisting of hydrogen, alkyl, aryland furyl, and R is a member of the group consisting of hydrogen, alkyl,and a-hydroxy-alkyl, said aldehyde having the general formula:

RCH=OOHO wherein R is a member of the group, aryl and alkyl, and R is amember of the group, aryl, hydrogen and alkyl, the substituentsR and Rrepresenting respectively the following combinations of groups and noothers: aryl and hydrogen, alkyl and alkyl, aryl and alkyl and aryl andaryl.

6. In a process for the production of 5-nitro-5-hydroxymethyl-2-styryl-1,3-dioxane, the step which comprises reactingcinnamic aldehyde with 'tris(hydroxymethyl)nitromethane in theprespropylacrolein in the presence of an acid ca1talyst.

MURRAY SENKUS;

Patent No. 2,553,622. August :28, 1915..

' Patent should be read with this correction therein t at th Sam may00nform to the record vof the case in the Patent Office.

CERTIFICATE OF. CORRECTION.

MURRAY SENKU$..-

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,first e-olumn, line 12, for "akyl" read a1ky1; page 2, first' column,line 56, I Example III, for (l-methy'l" read (l-e'thy1 and that the saidLetters Signed and sealed this 25th day of December, A. D. 19L 5.

Leslie Frazer (Seal) First Assistant Commissioner of Patents.

